Flow control valves can be used to regulate fluid flow through piping systems and the like. Proportional flow control valves can provide a regulated flow rate that is proportional to a control signal. A proportional flow control valve can include a regulating spool moveable by a solenoid to obtain an adjustable opening. A proportional valve can come in several different styles, such as, a surface-mounted valve, a sectional valve, and a cartridge-style valve, for example. In addition to a proportional valve, a pressure compensator can be used in a hydraulic system to provide a fairly constant flow over a range of pressures induced by different loads.
Systems of spool valves or poppet valves are known that use additional (or non-integral) check valves for load holding and load sensing/piloting. Other prior valve designs provide integral load holding capability by using check balls in poppets, such as that shown in and described in U.S. Pat. No. 6,328,275, but such designs can have multiple leak paths. Also known is a reverse flow check valve design used in a two-way, or on/off, valve, such as is commercially available from HydraForce, Inc. of Lincolnshire, Ill., as model number SVCV08-20, for example.
A continuing need exists for a three-way valve with a lowered leakage possibility and with inherent load holding capability. Additionally, a continuing need exists for economical solutions to the problem of finding integrated valve solutions that result in lower total costs when compared to a combination of valves with similar functionalities.